This invention is generally directed to developer compositions, and more specifically, the present invention relates to developer compositions with coated carrier components, or coated carrier particles that can be prepared by, for example, dry powder processes. More specifically, the present invention relates to compositions, especially carrier compositions comprised of a core and thereover polymers containing a quaternary ammonium salt functionality. The quaternary ammonium salt can be contained in a copolymer such as polymethylmethacrylate-co-polyvinylbenzyltriethyl ammonium chloride or a terpolymer such as polystyrene-co-poly-n-butylacrylate-co-polyvinylbenzyltriethyl ammonium chloride. Alternatively, the quaternary ammonium site may be formed by reacting a suitable amine-containing polymer with a suitable halogen-containing polymer to form a polymer crosslinked with quaternary ammonium sites, such as polystyrene-co-poly-(n-butylacrylate)-co-poly(vinylbenzyl chloride) reacted with poly(dimethylaminoethyl methacrylate)-co-polystyrene to form polymers crosslinked with quaternary ammonium salt sites.
The present invention relates to carrier particles comprised of a core with a coating thereover of a polymer containing quaternary ammonium salt sites. The substituents on the nitrogen of the ammonium salt site can be aliphatic like alkyl, aromatic like aryl, or mixtures thereof and the anion can be a halogen (Cl, F, Br, I), sulfate, phosphate, and the like. The backbone of the polymer can be polymers of one or more of the following styrene, n-butyl acrylate, butadiene, chloromethylstyrene, methylmethacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dibutylaminoethyl methacrylate, and the like. Alternatively, the ammonium salt containing polymer may be formed by reaction of two appropriate polymers to form a quaternary ammonium salt site. One polymer may be an amine containing polymer such as homopolymers or copolymers containing, for example, dialkylaminoalkyl methacrylates such as dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, diisopropylaminoethyl methacrylate, dibutylaminoethyl methacrylate. The second polymer contains sites that would react with the amine to form a crosslink, such as reactive halogens, for example homopolymers or copolymers of polyvinylbenzyl chloride (or fluoride, or iodide, or bromide), or allyl chloride (or fluoride, or iodide, or bromide). Moreover, the copolymer coating may contain a conductive component, such as carbon black, and which conductive component is preferably dispersed in the polymer coating. With the conductive component, there can be enabled, for example carriers with increased developer triboelectric response at relative humidities of from about 20 to about 90 percent, improved image quality performance, excellent high conductivity ranges of from about 10.sup.-10 to about 10.sup.-7 (ohm-cm).sup.-1, and the like. An advantage associated with the carriers of the present invention include a triboelectrical charge, for example a carrier tribo range of from about a plus (positive charge) 50 to about 150, or to about 95 microcoulombs per gram, and preferably from about a positive 55 to about a positive 90 microcoulombs per gram, and most preferably from a positive about 60 to a positive about 70 microcoulombs per gram.
The carrier particles of the present invention can be selected for a number of different xerographic copiers and printers, such as high speed color xerographic copies, printers, digital copiers, and more specifically wherein colored copies with excellent and substantially no background deposits are achievable in copiers, printers, digital copiers, and the combination of xerographic copiers and digital systems. Developer compositions comprised of the carrier particles illustrated herein and prepared, for example, by a dry coating process are generally useful in electrostatographic or electrophotographic imaging systems, especially xerographic imaging and printing processes, and digital processes. Additionally, the invention developer compositions comprised of substantially conductive carrier particles are useful in imaging methods wherein relatively constant conductivity parameters are desired. Furthermore, in the aforementioned imaging processes the triboelectric charge on the carrier particles can be preselected depending on the polymer composition and dispersant component applied to the carrier core and the type and amount of the conductive component selected.